Hydrodeoxygenation Activity Research Articles

Rational design of Ni-MoO3–x catalyst towards efficient hydrodeoxygenation of lignin-derived bio-oil into naphthenes

Design of a robust catalyst with high activity but the low cost for the hydrodeoxygenation (HDO) of bio-oils is of great importance to bring the biorefinery concept into reality. In this study, density functional theory (DFT) calculation was adopted to analyze the optimal location of Ni on MoO3–x containing oxygen vacancy, and the corresponding result demonstrated that metallic Ni cluster located at the neighborhood of oxygen vacancies would significantly evoke HDO activity. Enlightened by DFT results, NiMoO4 was first hydrothermally synthesized and then employed to fabricate Ni-MoO3–x catalyst via a low-temperature reduction, where Ni escaped from NiMoO4 and was reduced to its metallic state. Such an evolution of Ni species also induced the formation of oxygen vacancies around metallic Ni cluster. In the HDO of p-cresol, Ni-MoO3–x exhibited high activity with a complete conversion and a methylcyclohexane selectivity of 99.4% at 150 °C. Moreover, the catalyst showed good versatility in catalyzing HDO of diverse lignin-derived oxygenates and lignin oil. 2D HSQC NMR, gas chromatograph and elemental analysis of the lignin oil demonstrated the high deoxygenation efficiency and saturation of the benzene ring over Ni-MoO3–x. In the upgrading of crude lignin oil, the deoxygenation degree was up to 99%, and the overall carbon yield of the naphthenes was as high as 69.4%. Importantly, the structures and carbon numbers of the naphthene products are similar to jet fuel-range cycloalkanes, which are expected to have a high density that can be blended into jet fuel to raise the range (or payload) of airplanes. This work demonstrates the feasibility for improving the targeted catalytic reactivity by rational tailoring the catalyst structure under the guidance of theoretical analysis, and provides an energy-efficient route for the upgrading of lignin crude oil into valuable naphthenes.

Hydrodeoxygenation of safflower oil over cobalt-doped metal oxide catalysts for bio-aviation fuel production

The catalytic hydrodeoxygenation process provides an alternative route for the production of renewable jet fuel, which can directly replace petroleum-derived hydrocarbons. To this end, the catalytic performance of Co-based catalysts supported by different metal oxides, γ-Al2O3, TiO2, ZnO and ZrO2 was tested to evaluate their catalytic activity and product selectivity in hydrodeoxygenation of safflower oil. The results indicated that catalytic performance changed in response to acidity, morphologies and particle size of catalysts. Benefiting from these combined characteristics, Co/ZnO catalyst exhibited a highly catalytic activity, being capable of producing jet fuel-range hydrocarbon selectivity of 65.96% under reaction parameters of 350 °C of reaction temperature, 8 h of reaction time and 75 bar of H2 initial pressure. In addition to superior activity, the coke content of Co/ZnO was much lower compared to other employed catalysts thereby affecting the stability of the catalyst and resulting in less deactivation and coke formation.

Upcycling waste polycarbonate plastics into jet fuels over NiCo/C by catalytic tandem hydropyrolysis/hydrodeoxygenation

Chemical upcycling of waste polycarbonate (PC) into jet fuels through catalytic tandem hydropyrolysis/hydrodeoxygenation (THH) is a practical strategy to generate value from polymer wastes. A process which combining hydropyrolysis with vapor phase hydrodeoxygenation (HDO) was proposed in a two-stage pressurized fixed-bed reactor. A cobalt-based Metal-Organic Framework (MOF) derived material supported with nickel was designed for the vapor-phase HDO of phenolic compounds derived from PC hydropyrolysis. The product distribution could be regulated by optimizing reaction pressure in the reactor and catalyst to PC mass ratio. Experimental results showed that the products are all phenolic compounds in the absence of catalysts, while a high yield of jet-fuel range cycloalkanes (100%) was obtained under optimized conditions (7 bar H2 pressure and 5:1 catalyst to PC mass ratio) over NiCo/C. The high HDO activity of NiCo/C depends on the synergistic effect of nickel and cobalt atoms, which facilitates the elimination of phenolic hydroxyl group and hydrogenation of benzene ring. This work puts forward an efficient approach for upcycling PC waste into jet fuels with MOF-derived NiCo/C as a catalyst.

Catalytic hydropyrolysis of biomass over NiMo bimetallic carbon-based catalysts

Catalytic hydropyrolysis (CHP) is an emerging and promising technology to convert lignocellulosic biomass resources into alternative fuels and valuable chemicals. In this work, NiMo bimetallic carbon-based catalysts were designed and applied in the thermal conversion of alkaline lignin at 450 °C, 500 °C, and 550 °C under 1 atm H2. The CHP process exhibited a higher deoxygenation extent of around 60% compared with pyrolysis (FP) and hydropyrolysis (HP) processes. The bio-oil with higher H/C ratio and lower O/C ratio corresponding to a chemical formula of CH1.167O0.245 was obtained at 500 °C over the IW catalyst prepared via incipient wetness impregnation. CO2 and CO were generated via the decarboxylation and decarbonylation reactions, respectively. As for the CHP of real biomass, the deoxygenation extent reached about 55% over different modified catalysts. The ball milling-melting catalyst showed a considerable liquid product yield of 35.0 wt% and the best bio-oil quality with the chemical formula of CH1.456O0.339. The remarkable hydrodeoxygenation activity of carbon-derived catalysts was attributed to the synergistic effect of metallic Ni0 and intermediate oxidation state of Mo2+/Moδ+. The active hydrogen was adsorbed on the nickel sites, and the molybdenum species were responsible for eliminating the oxygen in aromatic oxygenates.

Hydrotreatment of pyrolysis bio-oil with non-edible carinata oil and poultry fat for producing transportation fuels

The cost of producing biofuels has been more expensive than fuels from fossil energy due to the heterogeneous nature of biomass sources. Therefore, commercialization efforts for producing biofuels have focused on blending with oleochemical feedstocks. This study carried out co-hydroprocessing (50:50) of pyrolysis oil with carinata oil or poultry fat over two catalyst supports. Cobalt and molybdenum catalysts supported on Douglas fir-derived biochar and alumina were used. The major goal of this study was to understand the synergistic effect of mixing pyrolysis oil with triglycerides for hydrotreatment under various supports, the influence on the oil quality, hydrodeoxygenation (HDO) and coke formation. The catalyst aided by biochar displayed improved HDO. Higher hydrogen consumption and low coke formation were seen for biochar support, and oxygen was predominantly removed via dehydration. Large oxygen-containing functional groups, high surface area, and acid sites in biochar might have made it a better HDO catalyst. Blending pyrolysis oil with poultry fat yielded better pyrolysis bio-oil quality over carinata oil and produced a higher percentage of jet fuel fraction. In summary, pyrolysis bio-oil mixed with poultry fat and hydrotreated using biochar support catalysts was more effective in HDO activity and improving overall pyrolysis bio-oil quality than alumina-supported catalyst and carinata oil.

Harvesting alkyl phenols from lignin monomers via selective hydrodeoxygenation under ambient pressure on Pd/α-MoC catalysts

Alkyl phenol is an essential chemical intermediate that is in high demand in the chemical industry. The synthesis of alkyl phenols from lignin-derived molecules is one of the most promising routes for utilizing biomass resources. Herein, we report the catalytic hydrodeoxygenation (HDO) of dihydroeugenol (DHE) to alkyl phenols over a highly dispersed Pd/α-MoC catalyst with a substrate conversion of 98% and a selectivity of 96% to alkyl phenols. The Pd/α-MoC catalyst prepared by co-precipitation and temperature-programmed carbonization exhibits exceptional HDO activity under mild conditions with a low H2 pressure (1–10 bars). The characterizations of the catalyst suggest that Pd are highly dispersed on the α-MoC matrix. The reaction mechanism was investigated using the substrate scope experiments. Under ambient pressure, the abundant oxygen vacancies and acidity sites on Pd/α-MoC enable the selective hydrodeoxygenation of lignin monomers.

Origin of strong metal-support interactions between Pt and anatase TiO2 facets for hydrodeoxygenation of m-cresol on Pt/TiO2 catalysts

Metal/reducible metal oxide catalysts are widely used in hydrodeoxygenation (HDO) reactions for upgrading bio-oil to produce chemicals and fuel components. Under such strong reducing condition, the strong metal-support interaction (SMSI) should take place, however, few work has been devoted to understand the effect of facet of metal oxide on the SMSI and its consequence on HDO performance. Herein, Pt supported on anatase TiO2 with varying dominative exposed facets of (101), (100) and (001) were prepared and tested in HDO of m-cresol at 350 °C and atmosphere H2 pressure. The degree of SMSI of Pt/TiO2 is strongly dependent on the facet of TiO2 when reduced at 350 °C, and the degree of encapsulation decreases following the order of Pt/TiO2-100 > Pt/TiO2-001 > Pt/TiO2-101. The encapsulation correlates well with the reduction degree of TiO2 and the location of oxygen vacancy, which are resulted from varied oxygen vacancy formation and anisotropic diffusion rates in different facets. The intermediate SMSI is achieved on TiO2-001, which creates the maximal density of Pt-Ov-Ti3+ sites at the interfacial perimeter of TiOx/Pt for deoxygenation of m-cresol, resulting in the highest reaction rate and turnover frequency (TOF) while the lowest activation energy (Ea). In contrast, the maximum SMSI on TiO2-100 leads to the lowest deoxygenation rate while the highest Ea. This work provides insight into facet dependent SMSI of Pt/TiO2 and indicates the HDO activity can be finely tailored by tuning the facet of TiO2.

Hierarchical pore-trapped and hydrogen-bonded phosphoric acid in Pd-supported zeolite for the efficient aqueous hydrodeoxygenation of lignin derivatives at ambient temperature

Developing an efficient and stable catalyst for the aqueous hydrodeoxygenation (HDO) of lignin derivatives at ambient temperature is highly desirable. Here, a novel Pd/PHS catalyst with the hierarchical structure was facilely constructed. Taking HDO of vanillin (VAN, a typical molecule of lignin derivatives) to 2-methoxy-4-methyl phenol (MMP) as a model reaction, >99% VAN conversion and 98.2% MMP yield can be achieved over Pd/PHS at ambient temperature in a water solvent, outperforming the recent works reported in the literature. We found that the hierarchal zeolitic structure could immobilize acidic P species in Pd/PHS via trapping and hydrogen-bonding, and these P species could greatly accelerate the conversion of reaction intermediate, enhancing the yield of MMP product. Pd/PHS also showed excellent activities in HDO of other lignin derivatives. We think this work will provide a new route to guide the design of stable catalyst for the efficient aqueous HDO of lignin derivatives to high value-added chemicals and biofuels at ambient temperature.

Selective hydrodeoxygenation of guaiacol to cyclohexanol over NixCoyAlz catalysts under mild conditions

Hydrodeoxygenation is one of the key steps to upgrade of biomass derived bio-oil into valuable biofuels and chemicals. Developing of highly reactive and cost-effective catalysts for bio-oil hydrodeoxygenation is highly desired. Layered NixCoyAlz catalyst was prepared using layered double hydroxide (LDH) as the precursors. The optimized Ni1Co3Al2-600 catalyst exhibits excellent catalytic performance for guaiacol hydrodeoxygenation. Guaiacol could completely converted with 90.0% of cyclohexanol selectivity under relatively mild reaction conditions. The XRD and HRTEM characterizations of the as prepared catalysts confirmed the formation of Ni-Co alloy and the XPS analysis revealed the strong interaction between Al species with both Ni and Co in catalyst Ni1Co3Al2-600, which should contribute to its high catalytic activity for guaiacol hydrodeoxygenation. Catalyst Ni1Co3Al2-600 also demonstrated excellent versatility for the hydrodeoxygenation reactions of guaiacyl and syringyl compounds as well as high stability. The results from this work could provide a new approach for the constructing of effective catalysts from non-noble metal LDHs.

Ru-MnOx Interaction for Efficient Hydrodeoxygenation of Levulinic Acid and Its Derivatives.

Metal-oxide interaction was widely observed in supported metal catalysts, playing a significant role in tuning the catalytic performance. Here, we reported that the interaction of Ru and MnOx was able to facilitate the hydrodeoxygenation of levulinic acid (LA) to 2-butanol with a high turnover frequency (1.99 × 106 h-1), turnover number (4411), and yield (98.8%). Moreover, this catalyst was capable of removing the hydroxymethyl group of lactones and diol with high yields of products. The high activity of the Ru-MnOx catalyst was due to the strong Ru-MnOx interaction, which facilitated reduction of Ru oxide to Ru0 and Mn oxide to Mn2+. The increased fractions of Ru0 and Mn2+ provided metal and Lewis acid sites, respectively, and therefore facilitated LA hydrodeoxygenation. A linear correlation between the hydrodeoxygenation activity of the Ru-MnOx catalyst and [Mn2+]ln([Ru0]) was observed.

Enhancing the anisole hydrodeoxygenation activity over Ni/Nb2O5−xby tuning the oxophilicity of the support

Ni/Nb2O5-H, preparedviathe hydrolysis method, possesses a higher number of oxygen vacancies and metal-support interface than Ni on commercial Nb2O5(Ni/Nb2O5-C), resulting in enhanced activity and selectivity towards deoxygenated products.

Hollow and mesoporous M@aluminosilicate (M = Rh, Pd and Pt) bifunctional catalytic nanoreactors for the hydrodeoxygenation of lignin-derived phenols

The high hydrodeoxygenation activity of Rh@Al2.0–mSiO2 could be attributable to the synergistic effect between the metallic Rh and Lewis and Brønsted acid sites.

Improving the hydrodeoxygenation activity of vanillin and its homologous compounds by employing MoO3-incorporated Co-BTC MOF-derived MoCoOx@C.

Lignin-derived aryl ethers and vanillin are essential platform chemicals that fulfil the demands for renewable aromatic compounds. Herein, an efficient heterogeneous catalyst is reported for reforming vanillin via a selective hydrodeoxygenation route to 2-methoxy-4-methyl phenol (MMP), a precursor to medicinal, food, and petrochemical industries. A series of MoCoOx@C catalysts were synthesized by decorating the Co-BTC MOF with different contents of MoO3 rods, followed by carbonization. Among these catalysts, MoCoOx@C-2 afforded ∼99% vanillin conversion and ∼99% MMP selectivity at 150 °C in 1.5 h in an aqueous medium. In contrast, CoOx@C afforded ∼75% vanillin conversion and ∼85% MMP selectivity. Detailed catalyst characterization revealed that CoOx and Co2Mo3O8 were the active species contributing to the higher activity of MoCoOx@C-2. The excellent H2-adsorption characteristics and acidity of MoCoOx@C-2 were beneficial to the hydrodeoxygenation of vanillin and other homologous compounds. The DFT adsorption energy calculations suggested the favourable interactions of vanillin and vanillyl alcohol with the Co2Mo3O8 sites in MoCoOx@C-2. The catalyst could be efficiently recycled 5 times, with a negligible loss in activity after the 5th cycle. These findings provide a systematic explication of the active sites of the mixed metal oxide-based MoCoOx@C-2 catalyst for the selective hydrodeoxygenation of vanillin to MMP, which is important for the academic and industrial catalysis community.

SBA-15-supported ultrastable Mo2N@CN catalysts for hydrodeoxygenation of guaiacol

Mo2N@NC/SBA-15 with high stability and dispersion were prepared by employing MoCl5 and dicyandiamide as Mo and C/N sources, respectively. Mo2N was in situ formed while dicyandiamide was converted to N-doped carbon (NC) during the carbonization process under H2 at an elevated temperature. The generation of ultrafine Mo2N nanoparticles (NPs) is attributed to N-doped carbon species around Mo2N NPs, which prevents the aggregation of Mo2N NPs at high carbonization temperature. Mo2N@NC/SBA-15 catalysts exhibit high hydrodeoxygenation activity and aromatic compound selectivity. Product distribution is heavily influenced by the conditions under which the reactions occur. High pressure and elevated temperature are optimal for the formation of aromatic products. At 380 °C and 2 MPa, the selectivity to aromatic products reached up to 92%, with the guaiacol conversion reaching 99%.

Boosting in-situ hydrodeoxygenation of fatty acids over a fine and oxygen-vacancy-rich NiAl catalyst

Hydrodeoxygenation (HDO) of fatty acids into long-chain alkanes for aviation fuels with alcohol hydrogen donor at mild condition over Ni-based catalyst is a practicable subject. However, highly active sites design for Ni-based catalyst remains significant challenges. Herein, a fine NiAl particle catalyst with numerous oxygen vacancy sites was fabricated via hydrothermal and reduction treatment. Introduction of small amount of Al species into Ni catalyst not only reduces the Ni particle size exposing plenty of active sites, but also generates oxygen vacancies in AlOx and sets up charge transfer in Ni-AlOx interfaces, thus guarantees the excellent in-situ HDO activity of fatty acids using isopropanol as hydrogen donor. Density functional theory calculation results further reveal that Ni (111) modified by AlOx with oxygen vacancy improves the charge density in Ni-AlOx interface and enhances the adsorption of fatty acid, facilitating the hydrodeoxygenation process. Benefiting from these attributes, Ni–Al0.33Ox presented superior catalytic activity and stability, which achieved 93.2% yield of n-heptadecane at 250 °C and was able to reuse at least 4 times. Therefore, the as-prepared Ni–Al0.33Ox is a promising Ni-based catalyst for alkanes production via in-situ HDO of fatty acids at mild conditions.

Comparison of Co-Mo-S and remote control model for designing efficient Co-doped MoS2 hydrodeoxygenation catalysts

Co-promoted MoS2 catalysts as good candidates can effectively remove the oxygen in bio-oil through the hydrodeoxygenation (HDO) of phenolics. However, it is of great importance to maximize the synergistic effect between Co and MoS2 which is conductive to the design of highly efficient Co-doped MoS2 HDO catalysts. Herein, two model catalysts with Co-Mo-S and CoS2/MoS2 (remote control model) as the active phases were successfully constructed and evaluated in the HDO of p-cresol. It was found that Co-Mo-S catalyst showed a significantly higher intrinsic HDO activity than CoS2/MoS2 catalyst, and the synergy factor between Co dopant and MoS2 of Co-Mo-S was 3.1 times that of CoS2/MoS2. The greatly enhanced HDO performance of Co-Mo-S catalyst is attributed to remarkably weakened strength of MoS bond, which can facilitate the sulfur vacancies (Vs) formation on the sulfur edges and promote the reaction rate of direct deoxygenation (DDO) pathway. This work revealed that Co-Mo-S model could better promote the CoMo synergy than the remote control model so as to design more efficient MoS2-based catalysts for HDO reactions.

Doping an Oxophilic Metal into a Metal Carbide: Unravelling the Synergy between the Microstructure of the Catalyst and Its Activity and Selectivity for Hydrodeoxygenation

Doping an Oxophilic Metal into a Metal Carbide: Unravelling the Synergy between the Microstructure of the Catalyst and Its Activity and Selectivity for Hydrodeoxygenation

The formation and transformation of hexadecanal influence on reaction pathway and activity in the palmitic acid hydrodeoxygenation over mesoporous ETS-10 supported Ni catalyst

Mesoporous ETS-10 zeolites supported Ni catalysts (Ni@NaMETS-10 and Ni@HMETS-10) were applied in the hydrodeoxygenation (HDO) of palmitic acid to investigate the formation and transformation pathways of hexadecanal (HAL) and reaction activity. Experiment results verified that HAL was an initial product in the HDO reaction under 0.1 MPa H2 pressure, and Ni@HMETS-10 exhibits higher activities (robs,1=2.55×10−4 mol kg−1 s−1, robs,2= 6.85×10−3 mol kg−1 s−1) than Ni@NaMETS-10 (robs,1=1.59×10−4 mol kg−1 s−1, robs,2=5.74×10−3 mol kg−1 s−1) due to the presence of Brönsted acid sites and highly dispersed Ni particles. At high H2 pressure (4.0 MPa), the acid-base properties of the support affected the transformation of HAL and the reaction pathways. The abundant Lewis basic sites on Ni@NaMETS-10 can promote the decarbonylation of the HAL and the HDCO route are dominate. Brönsted acid and Ni sites on Ni@HMETS-10 synergistically catalyzed the deoxygenation of palmitic acid via two parallel HDH2O and HDCO routes with a higher reaction rate (1.42×10−3 mol kg−1 s−1) than Ni@NaMETS-10 (1.31×10−3 mol kg−1 s−1). The reaction rate constants of each step in reaction routes on both catalysts were supplemented.

Hydrodeoxygenation of lignin biophenolics to cyclohexanes over sub-nanometric Ru multifunctional catalyst

Hydrodeoxygenation of lignin-derived phenolics into cyclohexanes is recognized as an attractive philosophy for producing high energy density fuels in a sustainable manner. Here, we report a catalyst made of low-loading, sub-nanoscaled Ru species and multifarious acidic centers on amorphous-silica-alumina, which shows excellent activity, selectivity, and stability in hydrodeoxygenation of 4-propylguaiacol to propylcyclohexane. Catalytic performance exhibits a linear relationship to the total acidities of this family catalysts, demonstrating a synergistic interaction between the metallic and acidic components. The superior performance of this catalyst allows the conversion of various lignin-derived monophenols, dimers, more significantly, a biophenolic stream from miscanthus lignin into cyclohexanes with high efficiency and yield. This work highlights the importance of the sub-nanometric size of Ru species in the advancement of efficient and affordable approaches towards lignin-based fuel production.

Trimetallic Cu-Ni-Re/Hβ catalyst for the direct conversion of furfural to 2-Methyltetrahydrofuran

The direct conversion of furfural (FUR) to 2-methyltetrahydrofuran (2-MTHF) was investigated over a trimetallic CuNiRe/Hβ catalyst. Under optimal reaction conditions at 240 °C under 3 MPa H2 for 1 h, almost complete conversion of FUR and high-yield of 2-MTHF (81 %) was achieved. This is the highest yield reported for the direct conversion of FUR to 2-MTHF. HR-TEM demonstrated that the growth of Cu nanoparticles (NPs) on the surface of Hβ was inhibited after loading Ni or Re resulted in the smaller Cu particle size and better hydrogenation and hydrodeoxygenation activity. H2-TPR characterization exhibited that the reducibility of bimetallic and trimetallic catalysts was higher than that of monometallic catalysts·NH3-TPD explained that Hβ acid sites mainly contributed to FUR deoxygenation. The adsorption configurations of FUR, furfuryl alcohol (FOL) and 2-methylfuran (2-MF) on the catalyst were revealed by ATR-IR. Catalyst evaluation and control experiments proved that FUR was first hydrogenated to FOL, followed by hydrodeoxygenation to 2-MF, and finally hydrogenated to 2-MTHF catalyzed by the combination of three metals.